The embodiment described herein generally relates to fixing members for securing components of an assembly, and particularly for securing such in an aircraft since such assemblies must be protected against the risks associated with lightning strikes.
The fixing element is generally mounted with moderate interference in the components of the assembly. It comprises a rod which is formed by a cylindrical shaft and an end which may or may not be threaded. The end of the shaft cooperates during assembly with, for example, a nut or a crimping ring.
During assembly with moderate interference, the cylindrical shaft has a diameter which is substantially larger than the hole that is produced in the components of the assembly and that are intended to receive the fixing element.
The assembly of such a fixing element in components must ensure good electrical conductivity between the fixing element and the components of the assembly. In particular, the electrical conductivity must be sufficient and compatible with the risks associated with lightning strikes, in particular, when the fixing element is intended for an aircraft assembly that is arranged near a fuel zone. For example, in the region of an aircraft wing.
When the electrical conductivity of the fixing element used is not sufficient, it is necessary to safeguard the fixing with respect to lightning by using a protection cap that covers the portion of the fixing element located at the side of the end that cooperates with a nut or a crimping ring. Such a protection cap (also called a “nut cap”) is shown and described in document WO 2012/118855. However, the use of a protection cap requires the production and the assembly of additional components, thus increasing the installation time of the fixing element and the weight associated with this fixing element, a critical aspect in aircraft applications.
Fixing elements are also known that provide good electrical conductivity as a result of the application of a surface treatment of the rod by means of anode oxidation. However, this surface treatment increases the installation forces required for assembling the fixing element in the hole with interference for the components to be assembled. Thus, the fixing elements which provide good electrical conductivity by means of anode oxidation of their surface are difficult to install. Thus, it is an object of the embodiments described herein to overcome at least one of the above-mentioned disadvantages. To this end, the embodiments relates to a fixing element for components of an assembly, comprising a rod that is formed by a cylindrical shaft and an end, the rod being a metal component that is at least partially surface-treated by means of anode oxidation.
The rod is coated over at least a portion of the cylindrical shaft with a lubricating coating.
Because of the association on the rod of the fixing element, a lubricating coating, and a surface portion that is treated by means of anode oxidation, it is possible to assemble, with interference, a fixing element that provides good electrical conductivity and thus good electrical continuity for the assembled components. Such a fixing element does not require the use of a protection cap to protect it from the risks associated with lightning strikes.
According to a first embodiment of the cylindrical shaft comprises at least a first strip that extends in the length of the cylindrical shaft and that is surface-treated by means of anode oxidation, and at least a second strip that extends in the length of the cylindrical shaft and which is coated with a lubricating coating.
In a further embodiment, the cylindrical shaft comprises a plurality of first strips that are surface-treated by means of anode oxidation and a plurality of second strips that are coated with a lubricating coating, the first and second strips extending over angular sectors that are distributed at the periphery of the cylindrical shaft.
In yet another embodiment, the first and second strips are distributed in a uniform manner at the periphery of the cylindrical shaft.
In a further embodiment, the cylindrical shaft comprises three first strips that are surface-treated by means of anode oxidation and that extends over three angular sectors of 45°, respectively, and that are separated in pairs by means of a second strip that is covered with the lubricating coating which extends over an angular sector of 75°.
In a still further embodiment, the cylindrical shaft comprises two first strips that are surface-treated by means of anode oxidation and extend over two angular sectors between 90 and 150°, respectively. Two second strips are covered with a lubricating coating which extends over two angular sectors between 30 and 90°, respectively.
The rod may be titanium and/or at least partially surface-treated by means of sulphuric anode oxidation. The lubricating coating may be a coating based on phenolic resin.
In a further embodiment, an assembly comprises at least two components which are fixed to each other by means of a fixing element.
These and other specific features and advantages will be further appreciated from the following description.